This invention relates to a detecting apparatus utilizing light beams for automatically guiding a vehicle along a predetermined track. Such a vehicle may be, for example, an automotive working vehicle or an unmanned conveyor cart in a factory. The detecting apparatus comprises means to emit beams of light toward a plurality of retroreflectors arranged along the track and adapted to reflect light in a direction from which the light strikes thereupon, and means to receive the beams of light reflected by the retroreflectors.
With this type of detecting apparatus beams of light per se are diffused by optical means, and the beams are emitted only in one direction. Such known apparatus have disadvantages as noted below and the improvement has been set forth.
Since beams of light per se are diffused by optical means such as a lens, the beams emitted toward the retroreflectors lose intensity and it is therefore necessary to provide a light source capable of emitting relatively strong beams of light. Where a plurality of retroreflectors are arranged in a row in a direction of directing the light beams, the reflected light beams returning from the retroreflectors are received simultaneously making it difficult to determine whether the received light beams are those reflected by the plurality of retroreflectors or by one of the retroreflectors. This has a disadvantage of requiring a complicated construction. Furthermore, for structural reasons the beams of light are not permitted to diffuse to a great extent, which has the disadvantage of requiring many retroreflectors arranged on the track even where a vehicle is guided along a straight track between two predetermined points. It is difficult to guide the vehicle along the tract if retroreflectors are arranged at wide intervals.
As shown in FIG. 20 of the accompanying drawings, the known detecting apparatus is prone to an error .DELTA..theta. in a detected angle of light reception in case the beams of light emitted from the apparatus diffuse in the horizontal direction including a direction (angle) to be detected. There is an inconvenience that this error greatly varies with variations in the distance between the detecting apparatus and retroreflectors CC.
In order to minimize the unnecessary horizontal diffusion of the beams of light emitted from the detecting apparatus, the conventional apparatus often employs means to emit laser beams which do not diffuse to a great extent or a plurality of lenses to prevent the diffusion, which results in a complicated and costly construction.